1. Field of the Invention
The present invention relates to a supply circuit for an apparatus which is provided with a supply voltage which is low relative to the amplitude of a main voltage supplied from a main power supply network. The main power supply line, is connected in series with a load, and the supply circuit is connected in parallel with a power-dissipating or resistance element that is connected in series with the load. The supply circuit supplies voltage to a switching apparatus that controls the switch for connecting and disconnecting the load to the main power supply.
2. Discussion of the Prior Art
A low voltage type of supply circuit is shown in the disclosure of French Pat. No. 2,449,922. In that patent a circuit having an ohmic, resistive power dissipating element is connected in series with the load and the main power supply line. The voltage drop across the ohmic resistance serves as the supply voltage for a constant-current circuit that recharges an accumulator. The accumulator provides the supply voltage for a time-controlled switching apparatus for respectively connecting or disconnecting the main power supply to the load (for example, an electrical heating member or a circulating pump). One special advantage of such a circuit is that the switching apparatus operates from a stored power supply and thus provides continuing operation during the outage of a main power supply voltage. In addition, with a disconnected load, it merely requires a two-wire connection, which is already provided by the switching line that supplies power to the load. Such a circuit eliminates the need for further modification of the main network during installation or operation of the switching apparatus. As a result, even installation in existing systems is enhanced and thus promotes conversion of a simple switching line to energy-saving heating-control systems.